One of the most amazing and useful adaptations that humans have is bipedalism. Our ancestors developed this adaptation as a necessity, possibly because of thinning forests or the need to carry their young. But how can we tell that one of these creatures walked on two feet? There are many ways to tell from the shape of bones, to their length. For me the most interesting difference that bipedalism makes is strangely enough in the skull. The foramen magnum is the hole at the base of the skull through which the spinal cord connects to the brain. In quadrupedal vertebrates this hole is at the back of the skull. This is true for our primate relatives as they walk on all fours most of the time. However, in humans the foramen magnum is at the base of the skull. This is due to our spine being vertical as opposed to horizontal. When we look at our hominin relatives we can see the shift from a horizontal spinal position to a vertical one.
great! there is so much of interest in the Formen Magnum. lots of great work coming out these days on how ot measure its placement and what it means. I just read this paper the other day (behind a paywall, but the abstract kinda tells the whole story!): https://www.sciencedirect.com/science/article/abs/pii/S0047248417300179
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